Method, session management function node, user plane function node, and user equipment for session management parameters maintenance and computer readable recording medium therein

ABSTRACT

The method proposes to establish at least one session between the User Equipment and the Session Management Function node, and initiate session deactivation for a session indicated by the User Plane Function node, upon detection inactivity of User Plane connection for the session for a period by the User Plane Function node.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 16/324,187 filed on Feb. 8, 2019, which is aNational Stage Entry of international application PCT/JP2017/036858filed on Oct. 11, 2017, which claims the benefit of priority fromEuropean Patent Application No. 16193391.6 filed on Oct. 11, 2016, thedisclosures of all of which are incorporated in their entirety byreference herein.

TECHNICAL FIELD

The present disclosure relates to a communication system. The disclosurehas particular but not exclusive relevance to wireless communicationsystems and devices thereof operating according to the 3rd GenerationPartnership Project (3GPP) standards or equivalents or derivativesthereof. The disclosure has particular although not exclusive relevanceto the so-called ‘Next Generation’ systems.

BACKGROUND ART General

The following terminologies are used within this document and can beapplied to any generation of mobile networks like 2G (GSM (Global Systemfor Mobile communications)), 3G (UMTS (Universal MobileTelecommunications System)), 4G (LTE (Long Term Evolution)/EPC (EvolvedPacket Core)), 5G (NR (New Radio)/NextGen (Next Generation)) or anyother. Taking an example, if “UE” is mentioned in the specification, itcan be any generation of UE.

The term UDM (Next Generation User Data Management), SDM (SubscriberDatabase Management) or AAA (Authentication Authorization Accounting)could be used synonymously to HSS (Home Subscriber Server)/HLR (HomeLocation Register) from 3G/4G. Such functional entities act as arepository where the UE's subscription data is stored and can becompared to an existing HSS or HLR or a combined entity.

Functional entities or network function used in this document asseparate entities could be also collocated together or even finerseparated in particular deployments or as described in the architecturefigures.

The terms ‘terminal’, or ‘device’, or ‘user terminal’ or ‘UE’ (UserEquipment) or ‘MT’ (Mobile Terminal) are used in an inter-exchangeablemanner where all of the terms express the similarly the equipment usedto send/receive data and signaling from the network or mobile network orradio access network.

The term “session” is used in the same meaning as “PDU (Protocol DataUnit) session” or “PDN (Packet Data Network) connection” or “APN (AccessPoint Name) connection” or “connection for a particular network slice”.The existing sessions are those sessions for which already a UE contextexists (is established) in the core network control plane and/or userplane and the UE itself. The “existing sessions” has the same meaning as“established PDU sessions” or “established PDN connections”. Eachsession can be identified with a “session ID (Identifier)”, which can besimilar to an “EPS (Evolved Packet System) bearer ID”, an “APN”, a“slice ID”, a “slice instance ID”, a “service ID” or any other temporaryor permanent identifier of a PDN connection or a PDU session or aservice used by the UE.

The term “connection” is used for the user plane connection where a kindof “path” is established to send the UL (Uplink) or the DL (Downlink)data between the UE and a user plane GW (Gateway) terminating the PDUsession. Depending on the context, a connection can be either the wholeuser plane path for a PDU session; or only a connection over a giveninterface, e.g. a connection over a radio interface, or a connectionover the NG3 interface (between a UPF (User Plane Function) in the NG CN(Next Generation Core Network) and the (R)AN ((Radio) Access Network)).

The following terminology for the procedures is used:

-   -   Session establishment: e.g. PDU session establishment where the        SM (Session Management) context exists (is established) in the        UE and in the NG CN control plane and/or user plane.    -   Session release: deletion of the PDU session, which means the SM        context is deleted (released) in the UE and in the NG CN control        plane and/or user plane.    -   Session/connection activation: activating the UP connection path        for session, for which the SM context exists in the UE and in        the NG CN.    -   Session/connection deactivation: deactivating the UP connection        path without deleting the SM context in the UE and in the NG CN.        With other words just releasing the UP connection.

The mobility states of the UE are called De-Registered,Registered-Standby (“Standby” for simplicity) and Registered-Ready(“Ready” for simplicity). These states are also called MM (MobilityManagement) states. Please note that there is a difference between themobility states (MM states) and session states (SM states).

Background

The telecommunication industry started to work on new generation ofnetwork referred as 5th generation (5G) networks. Activities in multipleresearch and standardization organizations were initiated to develop the5G network which shall offer services to multiple vertical serviceproviders and serving high variety of terminals. Especially 3GPP inactivities were initiated in the RAN area under the term “New Radio”(NR) and in the core network (CN) under the term “NextGen” (NG). Pleasenote that those terms will most probably change before the 5G system isintroduced to the market. Therefore terms like NG CN (or alternativelyNG AN) as used in this document have the meaning of any 5G CN or 5G ANtechnologies.

3GPP studies the NG system architecture, and corresponding issues andsolutions are captured in 3GPP Technical Report (TR) 23.799 [1]. FIG. 1describes the NG architecture for simultaneous access to multiple PDNconnections (called PDU sessions in the NG study), as agreed in [1] bythe time of writing. The upper part of the FIG. 1 shows an example forthe NG control plane (NG CN) including a subscriber database management(SDM) 34, a Policy Control function (PCF) 32 and Core Control functions(CCFs) 24. The NG CCF 24 includes among others a mobility managementfunction (MMF) and a session management function (SMF). The user plane(UP) function(s) are shows as a Core User plane function (NG UPF) 28/29,as there could be one or multiple UPFs per PDU session configured.Further information about the description of the interfaces and thenetwork functions can be found in 3GPP TR 23.799 clause 7.3 [1].

One main feature of a 5G system is called network slicing. The 5G usecases demand very diverse and sometimes extreme requirements. Thecurrent architecture utilizes a relatively monolithic network andtransport framework. Thus, it is anticipated that the currentarchitecture is not flexible and scalable enough to efficiently supporta wider range of business needs. To meet such needs, the 5G NG systemcan be “sliced” in multiple network instances which are referred asnetwork slice instances (NSI). The network slices can be referred aslogically separated networks where the resources (processing, storageand networking resources) for different network slices are isolated. Anetwork operator uses a Network Slice Template/Blueprint to create aNSI. A NSI provides the network characteristics which are required by aService Instance. One example of the network architecture allowing a UEto connect to multiple NSIs simultaneously is shown in FIG. 2, asdescribed in [1].

FIG. 2 shows (using solid lines) a first network slice type/category(e.g. for IoT services) and (using discontinuous/broken lines) a secondslice type (e.g. for broadband services). The first network slice typecan have multiple NSIs for particular 3rd party customers. This figureshows that the RAN is shared and network slicing is applied in the NGCN. However, in future network slicing the RAN is also possible wherethe RAN resources are sliced/isolated, either in baseband processing orin frequency spectrum or both.

[1] also describes the Common Control Network Functions (CCNF) 24 andthe Slice-specific Core Network Functions (SCNF) 23, as shown in detailin FIG. 3. The CCNF 24 may include fundamental control plane networkfunctions to support basic functions' operation common among the NSIs,for example:

-   -   Subscriber Authenticator,    -   Mobility Management,    -   Network Slice Instance Selector (NSI Selector),    -   NAS Routing Function, etc.

In general, the NG system design should enable the transmission of anykind of data. It is assumed that the NG system supports the followingPDU session types:

-   -   IP type (e.g. IPv4 or Ipv6 or both), or    -   non-IP session (any unstructured data) or    -   Ethernet type.

One further solution described in 3GPP TR 23.799 (in clause 6.4.3) isshown in FIG. 4. The UE 20 may establish multiple PDU Sessions to thesame data network in order to satisfy different connectivityrequirements of different applications (e.g. session continuity) thatrequire connectivity to the same data network. In this solution, the MMand SM functions are separated.

With this, one main concept is that multiple SM contexts can beavailable per MM context. Also, different session continuity types perPDU session are possible.

SUMMARY OF INVENTION Technical Problem

The scenario considered in this document is that a UE is attached to thenetwork and can be associated with multiple UP-GWs (UPFs). The differentUPFs can be (a) part of the same PDU session, or (b) part of differentPDU sessions, or (c) part of different network slice instances (NSIs).With other words, multiple NG3 connections (e.g. tunnels over NG3interface) between the (R)AN and the UPFs can be available.

One assumption in this document is that a UE's “session” (or also calleda “PDN connection” or a “PDU session” to a particular data network) canbe in the Idle (inactive) state or the Active (connected) state. In thissense the terms “Idle session” or “Active session” are used. If asession is in the “Idle” state, then there is no NG3 connection/tunnelestablished between the UPF and the (R)AN. If a session is in the“Active” state, then there is a NG3 connection/tunnel establishedbetween the UPF and the (R)AN. It is further assumed that for anestablished UE's session a Session Management Function (SMF) isinstantiated/configured in the control plane and corresponding one ormore UPFs are instantiated/configured in the user plane. Further detailsabout the Idle and Active session state of the CPF (Control PlaneFunction) and the UPF can be found below in the detailed description.

As it is assumed that a single Session Management Function (SMF) isconfigured (or instantiated) per PDU connection or NSI and also the UEis registered for multiple sessions, there is need to isolate thesession management due to the resource isolation per network slice. Withthis, the management of the session context needs to be isolated persession.

There are existing proposals of independent management of sessionstates. However, it is unclear how to derive and configure the sessionparameters for the various PDU sessions, e.g. QoS (Quality of Service)parameters, or UE/Session Inactivity timer value(s) in the (R)AN node,which can be a part of the CN-assisted RAN parameters. Also, in case offlow based QoS framework (e.g. section 6.2.2 in TR 23.799) it is unclearwhich is the network function(s) in the control plane to generate andinstall the QoS policy to the user plane nodes.

Further, in case of multiple UPFs configured per PDU session (e.g. forlocal data network and for central data network as shown in FIG. 1), itis unclear how to activate multiple NG3 tunnels with different sessionparameters simultaneously.

The present disclosure seeks to solve or at least alleviate the aboveproblems by reducing the required signaling for NG3 tunnel establishmentallowing the activation of a particular session out of multiple existingsessions.

Solution of Problem

As one aspect of the present disclosure, a Session Management Function(SMF) node comprising: a processor configured to process to establish atleast one session with a User Equipment (UE); and a receiver configuredto receive, from a User Plane Function (UPF) node, informationindicating inactivity of user data transfer for a session among the atleast one session for a period, and wherein the processor is furtherconfigured to process to initiate session deactivation for the sessionindicated by the UPF node is provided.

As another aspect of the present disclosure, a User Plane Function (UPF)node comprising: a processor configured to detect inactivity of userdata transfer for a session among at least one session between a UserEquipment (UE) and a Session Management Function (SMF) node, for aperiod; and a transmitter configured to transmit, to the SMF node,information for deactivation of User Plane (UP) connection for thesession based on detection of the inactivity is provided.

As another aspect of the present disclosure, a mobile communicationsystem comprising the UPF node and the SMF node is provided.

As another aspect of the present disclosure, a session management methodcomprising: establishing at least one session with a User Equipment(UE); receiving, from a User Plane Function (UPF) node, informationindicating inactivity of user data transfer for a session among the atleast one session for a period, and wherein initiating sessiondeactivation for the session indicated by the UPF node is provided.

As another aspect of the present disclosure, a User Equipment (UE)inactivity detecting method, comprising: detecting inactivity of userdata transfer for a session among at least one session between a UE anda Session Management Function (SMF) node for a period; and transmitting,to the SMF node, a message for deactivation of User Plane (UP)connection for the session based on detection of the inactivity isprovided.

As another aspect of the present disclosure, a non-transitory computerreadable recording medium recording a program, the program, whenexecuted by a processor of a computing device, causing the processor toexecute a session management method comprising: establishing at leastone session with a User Equipment (UE); and receiving, from a User PlaneFunction (UPF) node, information indicating inactivity of user datatransfer for a session among the at least one session for a period; andinitiating session deactivation for the session indicated by the UPFnode is provided.

As another aspect of the present disclosure, A non-transitory computerreadable recording medium recording a program, the program, whenexecuted by a processor of a computing device, causing the processor toexecute a User Equipment (UE) inactivity detecting method, comprising:detecting inactivity of user data transfer for a session among at leastone session between a UE and a Session Management Function (SMF) node,for a period; and transmitting, to the SMF node, information fordeactivation of User Plane (UP) connection for the session based ondetection of the inactivity is provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram for illustrating example non-roaming referencearchitecture for access to multiple PDU/PDN sessions to local andcentral data networks.

FIG. 2 is a diagram for illustrating example architecture of UEsconnecting to multiple network slices.

FIG. 3 is a diagram for illustrating example of common control planepart and slice specific part.

FIG. 4 is a diagram for illustrating example architecture for multiplesessions and sessions with multiple GWs for the same data network.

FIG. 5 is a diagram for illustrating assumed architecture showingmultiple network slices/PDU sessions (with corresponding multiplededicated CPFs).

FIG. 6 is a diagram for illustrating assumed architecture showing for asingle slices/PDU sessions.

FIG. 7 is a diagram for illustrating call flow for the PDU sessionestablishment procedure with session parameters exchange.

FIG. 8 is a diagram for illustrating call flow for the sessionparameters modification procedure during the UE is in MM active state.

FIG. 9 is a diagram for illustrating call flow for the sessionactivation procedure.

FIG. 10 is a diagram for illustrating call flow for the sessionactivation procedure where all existing PDU sessions are activated.

FIG. 11 is a general block diagram of the UE 20.

FIG. 12 is a general block diagram for the MMF 24.

FIG. 13 is a general block diagram for the SMF 26/27.

FIG. 14 is a general block diagram for the (R)AN node 22.

DESCRIPTION OF EMBODIMENT

For the purposes of this document the reference architecture from FIG. 1for a single established session (a network slice or a PDU session) isassumed. For multiple established sessions, FIG. 5 is introduced as anexemplary architecture where a UE 20 has established 2 differentsessions A and B. Please note that this is for exemplary purpose onlyand the number of sessions is not limited to two. The different sessionsmay belong to different network slices or to the same network slice buthaving multiple PDU sessions. In the control plane there is a boxdenoting common control network functions (CCNFs) 24 which are sharedamong network slices or PDU sessions. Such CCNFs 24 may include amobility management NF (called MMF), anAuthentication/Authorization/Security NF (network function), a NAS(Non-Access Stratum) signaling routing a NF and others. As it is shownin FIG. 5, each PDU session or network slice can have independentdedicated CPFs 38/39. The Dedicated CPFs 38/39 may include the followingexemplary network functionality:

-   -   Session Management network function (SMF): it is assumed in this        document that this function is responsible for the session        management for a specific session (a network slice, or a PDU        session).    -   CPF of a GW (aka GW-C of the UPF), as the CP (Control Plane) of        the GW is known as S/PGW-CP (Serving/PDN (Packet Data Network)        Gateway-Control Plane) function from the control/user plane        separation in EPC, called CUPS).    -   PCF: the complete or part of the PCF as described in FIG. 1.        This means that some parts of the PCF can be a part of the CCNF        and other parts can be part of the Dedicated CPF.    -   Authentication, Authorization and Security functions related to        the specific Network slice of the PDU session.

Each SMF has a signaling association with the UE's MMF. For eachestablished session, the MMF and the SMF know each other and can sendsignaling at any time independent of the UE's mobility or session state.Further, the CCNF 24 and the SMF exchange a UE ID or a subscriber ID(temporary or permanent) and use this ID in each signaling messageexchange in order to point to the corresponding UE's context in the CCNF24 or in the SMF.

In addition, a UPF (3GPP specified GW functionality e.g. to enforce QoSor traffic policies) per network slice or PDU session isconfigured/instantiated. Each of the (NG3) connections A or B can bemanaged independent, i.e. can be established, modified or releasedindependent from the other connections. Please note that there can beone or multiple UPFs. For example a UPF closer to the Edge can be usedas a mobility anchor and a UPF deeper in the CN can be used as an IPanchor (hosting the UE's IP address). For simplicity, in thisspecification a single UPF is used. However, the SMF is able toconfigure multiple UPFs if multiple UPFs are needed andinstantiated/configured for a given session.

One example shown in FIG. 5 is that there are 2 connections (e.g.tunnels over NG3) between a (R)AN node 22 and UPFs 30/31: a singleconnection for the slice/session A and the slice/session B. If tunnelingover NG3 is used per UE between the AN node and the UPFs A 30 or B 31,then there will be 2 tunnels established/modified/released each timewhen the UE transfers among the Standby<->Ready mobility state. Evenworse, if the tunneling over NG3 is per IP flow or per bearer then evenmore tunnels need to be established/modified/released for each Standbyand Ready mobility state transition.

The dedicated CPFs 38/39 can include a SMF and a Policy Control function(PCF). It is noted that the existence of the PCF in the dedicated CPFmay be based on the particular use case, e.g. for some network slicesthe PCF can be instantiated/configured per slice, whereas for othernetwork slices the PCF can be instantiated/configured as a common CP NF.

Solution 1

One main idea of this document is that the SMF maintains the PDU sessionparameters based on exchange with multiple other control plane corenetwork entities. The “maintaining” of session parameters is assumed toinclude the actions like e.g. the SMF retrieves the subscription orother temporary user parameters from other CN CP NFs, the SMF derivesnew session parameters or parameter values, or the SMF dynamicallymodifies the values of the parameters and signals those parameters tothe involved UP and/or CP NFs in the core network and the accessnetwork. The SMF also considers the UE'scapabilities/preferences/information indicated by the UE in the NASsession management signaling request to the SMF. The PDU sessionparameters are derived by the SMF per session for all impacted (UP) NFs,i.e. if a UE has multiple sessions with different SMFs, then those SMFscreate different sets of PDU session parameters based on the differentsession requirements.

The SMF provides the session parameters to the MMF at session (i.e. UPconnection) activation for a particular PDU session. The MMF can usethese session parameters to generate the UE context which is sent to the(R)AN node. For comparison purposes, in the 4G LTE/EPC the procedure forsending the UE context from a MME (Mobility Management Entity) to an eNB(evolved NodeB) is called “Initial Context Setup procedure” which alsoestablishes the E-RAB (E-UTRAN (Evolved Universal Terrestrial RadioAccess Network) Radio Access Bearer) context in the eNB. The differenceto this document is that in this document the session context, which isa part of the whole UE context, for a particular UP connection(including the RAB (Radio Access Bearer) and the NG3 tunnel connection)comes from the SMF. With other words, the CCNF (e.g. the MMF) generatesthe UE context to be sent to the (R)AN node based on the indication andinformation (session context) sent from the SMF.

FIG. 6 shows the assumed network architecture for a single PDU sessionwhere the common and the dedicated CP NFs are not separated explicitlyand depicted as a whole system 1. The common NG CN NFs can be forexample the MMF 25, the ASR (Authentication Server and CredentialRepository) 42, (the SCM (Security Context Management)+the SEA (SecurityAnchor Function)) 40, the U/SDM 34, and the SCEF (Service CapabilityExposure Function) 36. The dedicated NG CN NFs can be the SMF 26, theUPF 28/29 and the PCF 32. It is possible that the CPF is also a commonCN CP NF. According to the main idea above, the SMF 26 is a centralnetwork function to retrieve and derive the session parameters takinginto account the subscription parameters (the U/SDM 34), policy rules(the PCF 32) and communication parameters from external entities (overthe SCEF 36).

FIG. 7 shows a session establishment procedure. The main principles ofthe proposed solution are:

-   -   The SMF1 26 retrieves session (e.g. DNN (Data Network        Name)/APN-related) subscription information or dynamically        generated information from the U/SDM 34, the PCF 32 or the SCEF        36.        -   In case the SMF1 26 obtains information via the SCEF 36, the            SMF1 26 and the SCEF 36 discover each other (if needed) and            handshake during session establishment. In addition, the            SMF1 26 considers the information received from the UE 20            (e.g. during a NAS SM request) and received from the CCNF 24            (e.g. the MMF) about UE capabilities or preferences.        -   The SMF1 26 derives or updates or modifies session            parameters (e.g. QoS rules, charging rules, QoS parameters            and/or multiple Inactivity timer(s)). The SMF1 26 can update            or modify or newly determine session parameters at any time            implicitly, i.e. without retrieval of new information from            other CN CP NFs. The SMF1 26 coordinates and synchronizes            the states of the different NFs per session, especially the            inactive state transition.

For example, the SMF1 26 may store a communication pattern indicatingthe different UE behaviour or Application behaviour at various times ina given interval, e.g. day or week days.

-   -   The SMF1 26 may decide to derive a single or multiple UPFs for        the PDU session based on the information received from the U/SDM        34, the PCF 32 or the SCEF 36.    -   The SMF1 26 sends currently valid session parameters to the        (R)AN node 22 (via the MMF 24). The SMF1 26 may also install at        each session Activation such Session parameters to the UPF 28/29        during session establishment, or send them to the UPF 28/29 each        time at session/NG3 activation.

The steps from FIG. 7 are described in detail as follows:

Step (0): This is an optional step where the 3GPP external entities likea SCS/AS (Service Capability Server/Application Server) can indicate tothe SCEF 36 particular communication characteristics of a UE 20 or for aspecific Application. The communication between the SCS/AS and the SCEF36, as well as the authentication of the exchange with the HSS (or theU/SDM 34) is described in 3GPP TS23.682. It is assumed that the SCEF 36or alternatively the U/SDM 34 can store the received communicationcharacteristics and can associate the communication characteristics witha particular session ID (e.g. an APN from the 3G/4G systems).

Step (1): The UE 20 initiates radio connection and NAS connectionestablishment procedures. Besides the usual parameters included by theUE 20 in the NAS MM message (e.g. the UE ID, capabilities, preferences,etc.) the UE 20 includes a new capability indication about the support(or non-support) of one-to-one mapping of radio connections (RAB/DRB(Data Radio Bearer)) and existing NAS Session management contexts. Withother words, the UE 20 includes the new capability indication forindicating whether the UE 20 supports the feature of establishing e.g. asingle RAB/DRB to a particular existing NAS SM context whereas multipleNAS SM contexts (for multiple PDU sessions). For example, a UE 20implementing Release-13 LTE would expect that a RAB/DRB is establishedfor each existing NAS ESM (EPS Session Management) context. However, aUE 20 implementing Rel-15/16 LTE or New Radio technology can support thefeature of “independent Session UP activation” meaning that UPconnections can be activated or deactivated per PDU session withoutdeleting the NAS SM context. One example name of such new capabilityindication can be “individual SM activation” or “separate SM activation”if the UE 20 supports this feature. An example impact of this new UE'sindication is shown in solution 3, FIG. 10.

Step (2): The UE 20 initiates a Session setup procedure, e.g. by sendinga NAS Session setup request message to the NG CN. Such a message can beconsidered as a NAS session management (SM) message. Please note thatthe NAS Session setup request message may be encapsulated within the NASMM message like e.g. an Attach request message (i.e. may not be astandalone message).

Although the NAS Session setup request message is sent from the UE 20and is terminated at the SMF1 26, the message traverses (e.g. isforwarded over) a common NAS termination entity in the CCNF 24 (e.g. theMMF). The CCNF 24 can process the message (e.g. determine thedestination SMF entity) and select a proper SMF1 26 where to forward themessage. The CCNF 24 (e.g. the MMF or the NAS termination function) caninclude additional UE information towards the SMF1 26 to help the SMF126 to correctly process the NAS SM message (as exemplary shown in step2.1). For example the CCNF 24 (MMF) can encapsulate or piggyback the NASSession setup request message into another NG11 interface message whichfor exemplary purposes is shown as a Create Session request message instep 2.1. The Create Session request message contains, in addition tothe NAS Session setup request, at least one or multiple of the followingparameters: UE information like temporary or permanent subscriber IDs ordevice IDs (e.g. an IMSI (International Mobile Subscriber Identity), aTMSI (Temporary Mobile Subscriber Identity), a MSISDN (Mobile SubscriberIntegrated Services Digital Network Number)), a signaling exchangereference ID, a PDU session or a bearer ID, etc. The NAS Session setuprequest message from the UE 20 contains information like PDU sessiontype (e.g. IPv4, IPv6, non-IP or Ethernet, etc.) and the Session/Servicecontinuity type(s) (e.g. type 1, type 2 and/or type 3) for this PDUsession. The SMF1 26 uses this information to refer the signalinginteraction with the MMF 24 and also uses the information for thesignaling exchange with other CN CP/UP NFs.

Step (3): The SMF1 26 receives the request from the UE 20, validates themessage and determines the corresponding NG CN NFs which can serve thisUE's session. The SMF1 26 retrieves UE's session-related static ordynamic subscription context from the U/SDM 34. For this purpose theSMF1 26 is either pre-configured with the U/SDM address (or ID), or theSMF1 26 receives the U/SDM address (or ID) from the MMF 24, or the SMF126 discovers the U/SDM address (or ID) using e.g. DNS resolution. Forthe interaction with the SCEF 36, the U/SDM 34 and the SCEF 36 mighthave established an association with each other as described in (0.1).The U/SDM 34 may store the parameters/information received from the SCEF36 in particular DNN/APN-related session subscription information.

It is possible that the (PDU) session-related subscription parametersfrom the U/SDM 34 contain information about an SCEF 36 associated withthis PDU session. The SMF1 26 learns about (i) the SCEF identity and(ii) whether to contact the SCEF 36 directly or whether thecommunication exchange goes over the U/SDM 34. If needed, the SCEF 36and SMF1 26 establish a direct association for the exchange and/orupdate of session parameters. For example the SMF1 26 initiates a Createconnection request (or Association establishment) procedure as shown instep (3.1). This procedure can be similar to the T6a/T6b connectionestablishment procedure between the MME and the SCEF from TS23.682. Thedifference to the existing procedure in TS23.682 is that the SMF<->SCEFconnection/association is established for a session update for aparticular PDU session, whereas in the association is established fornon-IP data transmission.

Step (4): If required (based on type of a PDU session and/orsubscription information and/or local policies in the SMF1 26), the SMF126 selects a PCF 32 and retrieves policy rules and/or charging rulesinformation for the PDU session. The policy rule information can be adynamic rule or a pre-defined rule which is mapped in the SMF1 26 toe.g. known QoS/priority rules.

Step (5): Based on input from the subscription information and thepolicy rules, the SMF1 26 derives session parameters for the particularPDU session. An example about session parameters' details is listedbelow after the description of this call flow in NOTE 1. In addition theSMF1 26 selects the UPF(s) 28/29 to serve the PDU session. For example,the SMF1 26 can select a local UPF and a central UPF if the PDU sessionallows for both local and central traffic routing.

Step (6): The SMF1 26 performs a resource reservation procedure with theselected UPF(s) over the NG4 interface. This procedure can be similar tothe Sx Session Establishment Procedure as described in TS23.214. Theresource reservation procedure, or alternatively the Sx SessionEstablishment Procedure, is performed per UPF.

The SMF1 26 can determine one or multiple Inactivity timers to beapplied to the UPF 28/29 for different purposes. These Inactivitytimers, together with other parameters, are sent to the UPF1 28. Detailsabout the Inactivity timer(s) installed in the UPF 28/29 can be foundbelow in NOTE 2.

In addition, the SMF1 26 creates and sends to the UPF 28/29 the QoSpolicy (e.g. marking rules or filters) for the data packets. Oneparticular example is the case of Flow based QoS architecture. Pleasesee NOTE 3.

Step (7): After successful establishment of the UPF session over NG4interface, the SMF1 26 initiates a resource reservation procedure withthe (R)AN node 22. This procedure is performed over the CCNF 24 (e.g.the MMF). The SMF1 26 sends the session context parameters directly tothe RAN node 22, however, the SMF1 26 may not necessarily know the RANnode destination ID. Thus, the SMF1 26 may direct the message in step(7) to the MMF 24 and the MMF 24 forwards the message (e.g. withoutchanging the session context parameters) further to the RAN node 22.This message contains one or multiple of the following parameters: UEID(s), Session ID(s), QoS parameters, UPF ID(s), Inactivity timer(s).Please see NOTE 1 below for a complete list of session parameters.

The SMF1 26 provides the session parameters info to the (R)AN node 22over NG2 interface to indicate to the (R)AN node 22 how to manage theQoS policy (e.g. scheduling of differently marked packets) of the UPpackets coming from the UPF(s) 28/29. Please see NOTE 3.

Step (8): After the successful resource reservation procedure with the(R)AN node 22, the SMF1 26 replies to step (2) to the UE 20 with aSession setup response message. The Session setup response message canbe referred as a NAS SM message and the Session setup response messagecontains some session parameters (e.g. QoS parameters) to be used by theUE 20 in the uplink communication.

After step (8), the radio access connection/bearer and the NG3connection/tunnel are established and the UL and DL packets can betransmitted.

NOTE 1: An example list of session (context) parameters maintained atthe SMF is shown below. Please note that this list is non-exhaustive andnot limited to the mentioned parameters as list of parameters, but aswell as names:

(1) UE identifiers (temporary or permanent, optionally includingsubscriber identifiers) and session identifier(s);

(2) Traffic/packet/flow/service priority (or multiple priorities);

(3) The flow/service level (i.e., per service data flow, SDF (ServiceData Flow), or per SDF aggregate), and QoS parameters includes the QCI(QoS class identifier), the ARP (allocation and retention priority), theGBR (guaranteed bit rate), and the MBR (maximum bit rate). Theseparameters may include some of the parameters listed in other bullets inthis bulleted list.

(4) Packet Delay;

(5) Data rates valid for the whole PDU session (which can be similar,same or different from bullet (3)): AMBR (aggregate maximum bit rate). Anew proposed parameter is to have an AMBR per configured/used UPF. Incase of multiple UPFs, the SMF may determine an AMBR per UPF, and theSMF can assign the value to each UPF;

(6) Communication pattern for the application(s) using this PDUsession=>e.g. Session Inactivity timer (for the Idle state), RANInactivity/Dormant timer (for the RAN Inactive/Dormant state), one ormore types of UPF Inactivity timers;

(7) One or multiple UPF IDs (an IP address, a tunnel endpoint ID, etc.);and

(8) etc.

NOTE 2: The SMF can generate different types of CN UP Inactivity timersused for different purposes:

-   -   One type can be the Inactivity timer for the deactivation of the        UP connection (deactivation of PDU session), but still keeping        the PDU session context in the UE and the NG CN NFs (e.g. the        SMF and/or the UPF). Such first type of the Inactivity timer can        be exemplary called “UP Inactivity timer” meaning to trigger the        UP connection deactivation. Once the UP Inactivity timer expires        in the UPFs, then the UPF triggers the SMF to deactivate the UP        connection, i.e. to deactivate the (R)AN access connection and        the NG3 tunnel/connection. The session parameters/context is        kept in the UE and the NG CN NFs (e.g. the SMF, and/or the UPF).    -   Another type of the Inactivity timer can be to release the PDU        session, which would mean the release of the PDU session context        in the UE and the NG CN NFs (e.g. the SMF and/or the UPF). Such        second type of the inactivity timer can be exemplary called        “Session Inactivity timer”, meaning to trigger the complete        session release. Once the Session Inactivity timer expires in        the UPFs, then the session is terminated and the context is        removed, as well as the packet flow/bearer filters on the NG3,        the NG6 and the NG9 reference points. The UPF trigger the SMF to        release the PDU session including all SM states in the UE and        other (R)AN nodes and NG CN NFs.

Please note that the configuration of any session context parameters,and in particular “Session Inactivity timer”, “RAN Inactivity/Dormanttimer”, “UP Inactivity timer”, or “Session Inactivity timer” by the SMF126 can be also based on information received from an Application serveror a service platform (e.g. the SCS/AS) over the SCEF 36. The SMF1 26matches the information received from an SCEF 36 to a particular PDUsession context based on a UE ID and/or a session ID like DNN or APN asduring step (4) in FIG. 7.

The SMF synchronizes and manages the SM states in the UE, the UPFs andthe (R)AN nodes. Wherever the SMF recognizes a mismatch, e.g. one NF hasa timing mismatch and does not send the deactivation request in time tothe SMF. When the UE is getting in active mode gain for this session,the CCNF assigns a new SMF and the procedure is performed as describedabove. The SMF may select other UPFs, e.g. based on current loadsituation.

It is possible to group the above session parameters per UPF. Forexample, if a PDU session is configured with 2 UPFs 28/29 as shown inFIG. 1, the SMF can generate a session parameters set per UPF, in thiscase, 2 session parameters sets for the UPF1 28 and the UPF2 29. Thesignaling message from the SMF towards the (R)AN node 22 over the MMFneeds to implement a corresponding structure and identifiers, so thatthe (R)AN node 22 applies the session parameters correctly per UPF. Thiswould result in modified signaling messages in step (7) in FIG. 7. Forexample, the structure of the signaling message can be like:

Resource reservation request (e.g. towards the RAN node 22)

-   -   a Session ID    -   the UPF ID #1        -   info for NG3 tunnel establishment, e.g. an IP address, a            tunnelling endpoint ID and/or a transport layer port ID        -   [List of session parameters as described in NOTE 1]. Please            note that any parameter from the list can be used or            combined with others.        -   Traffic/flow filter rules to be applied at the (R)AN node,            e.g. how does the (R)AN node decide which the UL traffic to            send over the NG3 tunnel to the UPF ID #1.        -   (optionally) UE's support of “individual SM activation”            (this is needed in cases that such indication is not            transmitted directly from the UE to the (R)AN node, e.g. in            the RRC signaling, or not transmitted from the CCNF (e.g.            the MMF) to the (R)AN node over the NG2 interface as part of            the UE context setup procedure).        -   Etc.    -   the UPF ID #2        -   info for NG3 tunnel establishment, e.g. an IP address, a            tunnelling endpoint ID and/or a transport layer port ID        -   [List of session parameters as described in NOTE 1].        -   Traffic/flow filter rules to be applied at the (R)AN node,            e.g. how does the (R)AN node decide which the UL traffic to            send over the NG3 tunnel to the UPF ID #1.        -   (optionally) UE's support of “individual SM activation”            (this is needed in cases that such indication is not            transmitted directly from the UE to the (R)AN node, e.g. in            the RRC signaling, or not transmitted from the CCNF (e.g.            the MMF) to the (R)AN node over the NG2 interface as part of            the UE context setup procedure).        -   Etc.

Please note that the above parameters are applied in case of having asingle (radio) access connection, e.g. a single RAB or DRB, and multipleNG3 connections/tunnels between the (R)AN node and the UPFs of the same(PDU) Session. In such a case, in the DL, the (R)AN node merges thetraffic from all UPFs belonging to the same Session ID on the singleRAB/DRB. In the UL, however, the (R)AN node needs to decide which packetto route over which NG3 tunnel. In order to make the decision, theparameters listed above contain the parameter “traffic/flow filterrules” in order to configuring the UL routing table in the (R)AN node.

It is also possible that the (R)AN node establishes a RAB/DRB per NG3tunnel within the same (PDU) Session. In such a case, the mappingbetween the RAB/DRB and the NG3 tunnel can be 1-to-1. Since the mappingis “1-to-1”, the (R)AN node does not need to know “traffic/flow filterrules”.

To summarize, the SMF may or may not generate and include the sessionparameter “traffic/flow filter rules” towards the (R)AN node, dependingon the network configuration or the session configuration or the RANcapability.

Please also note that the grouping of session parameters per UPF can bealso sent from the SMF1 26 to the UE 20 during the session establishmentprocedure (e.g. during step (8) in FIG. 7), however not including theUPF ID(s), as the UE 20 may not need to know the UPF's IP address ortunnel IDs. The SMF1 26 may decide to send the session contextparameters in a “per UPF grouped manner” in case that the network (theRAN and/or the CN) has decided to establish a RAB/DRB per NG3 tunnel. Insuch a case the UE 20 maintains a kind of tree-structure if sessionmanagement context parameters, meaning to a PDU session, might bemultiple sets of session context parameters which can be compared tomultiple bearer context for a single PDN connection in the 4G LTE/EPCsystem.

Please note that for the same PDU session, the SMF1 26 generatesdifferent sets of session context parameters to the (R)AN node 22 (e.g.in step (7) in FIG. 7) and to the UE 20 (e.g. in step (8) in FIG. 7).The session context parameters are different, as the purposes to bereached in the UE 20 and in the (R)AN node 22 are different.

NOTE 3: SMF1 26 as coordination point for Flow based QoS architecture

In the so called Flow based QoS architecture, there can be multiple QoSflows within the same PDU session and possibly within the same RAB/DRB(the assumption is that a single RAB/DRB and a single NG3connection/tunnel carries multiple QoS flows). Basically, the NG CNrequests the (R)AN to carry different QoS flows within the same PDUsession and possibly over the same DRB. If such a QoS architecture isdeployed, this document proposes to use the SMF1 26 as the coordinationpoint/entity between the UPF 28/29 in the CN and the (R)AN. The SMF1 26creates the QoS marking rules towards the UPF(s) and the SMF1 26 alsocreates the corresponding session information and signals it towards the(R)AN node 22. In particular, taking for example the FIG. 7, in step(6), the SMF1 26 provides the QoS marking rules to the UPF(s) over theNG4 interface. Then, in step (7) in FIG. 7, the SMF1 26 providesinformation (e.g. with the session parameters) to the (R)AN node 22 overthe NG2 interface how to manage the QoS marking of the data packetscoming over the NG3 tunnel from the UPF(s).

FIG. 8 shows a session establishment procedure where session parametermodification can be performed while the UE 20 is in the MMConnected/Active state, e.g. if the session parameters modification isbased on indication from a 3GPP external application server (SCS/AS)over the service capability exposure function (SCEF) 36.

The steps from FIG. 8 are described in detail as follows:

Step (1) to step (8) are the same as in FIG. 7.

Step (9): Similar to step (0) from FIG. 7.

Step (10): If the UE (session) context in the U/SDM 34 is updated andthe U/SDM 34 has an active association with a SMF1 26 for this (session)context, the U/SDM 34 initiates an Update session context proceduretowards the SMF1 26. In this procedure the U/SDM 34 sends the updatedsession parameters to the SMF1 26.

Alternatively, it is possible that the SCEF 36 has an association withthe SMF1 26. This is shown as alternative step 10.1 in FIG. 8. In such acase, the SCEF 36 can perform the Update session context proceduredirectly with the SMF1 26. The U/SDM 34 may or may not be updated. Incase that the U/SDM 34 is not updated as part of an alternative step10.1, then the SMF1 26 may send the recent session parameters to theU/SDM 34 during the PDU session release procedure.

Step (11): If the session parameters in the SMF1 26 has been updatedwhile the SMF1 26 is in the Active SM state (meaning that the UE 20 isin the MM Connected/Active state), the SMF1 26 performs a resourcemodification procedure (alternative name for the procedure can be aSession modification procedure). During the Session modificationprocedure, the SMF1 26 sends the new session parameters to the UPFentity(s) 28/29.

Step (12): The SMF1 26 performs a Session update procedure (alternativename for the procedure can be a Session modification procedure) towardsthe (R)AN node 22. During the Session update procedure the SMF1 26 sendsthe new session parameters to the (R)AN node 22, as the signaling pathcan pass the CCNF 24 (e.g. the MMF).

Step (13): The SMF1 26 sends a Session modification request messagetowards the UE 20. This message can be considered as a NAS SM message.The SMF1 26 informs the UE 20 about the modified session parameters forthe uplink transmission.

Step (14): The UE 20 replies with a Session modification responsemessage towards the SMF1 26. This message can be considered as a NAS SMmessage.

FIG. 7 and FIG. 8 show the session parameters maintenance and exchangein case of the PDU session establishment procedure (FIG. 7) and thesession modification procedure (FIG. 8). However, it is possible togenerate session parameters during other procedure, e.g. during sessionactivation (i.e. UP connection activation) as shown in FIG. 9.

The steps from FIG. 9 are described in detail as follows:

Step (0): DL data arrives at the UPF1 28. It is assumed that the SMstate for this PDU session is Idle, so that the UPF1 28 cannot transmitthe DL packet.

Step (1): The UPF1 28 initiates a Session activation procedure towardsthe associated SMF1 26.

Step (2): The SMF1 26 may already maintain session parameters derivedduring the PDU session establishment as described in step (5) in FIG. 7,however, it is possible that some conditions might have changed and theSMF1 26 may determine new session parameters. Such new determination ofsession parameters can be based on the current day/week time and theavailability of communication pattern.

Step (3): The SMF1 26 performs an Activation session procedure, whichcan be similar to the resource reservation procedure from step (7) inFIG. 7.

Step (4): Depending on the MM state of the UE 20 (e.g. the UE 20 can bein the Idle or in the Connected state), the MMF 24 performs differentprocedures. For example, if the MM state is connected, as the NASsignaling connection and the NG2 signaling connection exist, the MMF 24forwards the SMF's request further to the (R)AN node 22. Otherwise, ifthe UE 20 is in the MM Idle state, the MMF 24 needs first to page the UE20 and later to setup the UE context to the (R)AN node 22.

Step (5): After the (R)AN node 22 receives the updated UE contextparameters, which can be in the form of the session parameters sent fromthe SMF1 26, the (R)AN node 22 establishes the new radio accessconnection (e.g. the radio access bearer) and updates its RANparameters. Possible update of the RAN parameters is described insolution 2.

Step (6): The MMF 24 replies to step (3) with a Session activationresponse message which is a response to step (3). This message containsthe RAN node UP identifiers (an IP address, tunnel endpoint identifiers,etc.).

Step (7): In case of the successful response in step (6), i.e.successful session activation in the (R)AN node 22, the SMF1 26 sends aSession Activation response message to the UPF1 28 including sessionparameters like QoS rules, charging rules, RAN UP IDs, etc. The sessionparameters may include among others one or multiple Inactivity timertypes which is used to determine the inactivity of a session as whole orto deactivate the UP connection merely (as described in NOTE 2 above).In some point of time, when the Inactivity timer expires, the UPF1 28can trigger a session deactivation request towards the SMF1 26. Pleasenote that the session deactivation request in not shown in FIG. 9.

If the indication in step (6) was not successful, the SMF1 26 sends aSession Activation response message to the UPF1 28 including acorresponding failure cause.

In case that multiple UPFs 28/29 are configured per PDU session, asalready explained, the SMF1 26 can generate and install differentsession parameters to the different UPFs. The different sessionparameters can include different Inactivity timers. However, if a common(radio) access bearer is used in the (R)AN system, then even if one UPFwould trigger the Session deactivation request towards the SMF1 26, theSMF1 26 should not deactivate the UP connection, as the data flows overthe other(s) UPF continue to use the connection.

Solution 2

One particular aspect which deserves a special attention is theindication of CN-assisted (R)AN parameters. Similar to the LTE/EPC, theNG CN can indicate (R)AN-related parameters to be taken into account bythe (R)AN for optimizing the UE power consumptions or for reducing theRAN-CN signaling. In the NG CN, such indication from the NG CN towardsthe NG (R)AN can be called e.g. “CN-assisted (R)AN parameters”. The“CN-assisted (R)AN parameters” can contain UE-related (R)AN parametersor Session-related (R)AN parameters. Also, “CN-assisted (R)ANparameters” can be determined and sourced from the MMF or from the SMF.The difference to the LTE/EPC system is that in the NG system the“CN-assisted (R)AN parameters” are stored in multiple network functions,whereas in the LTE/EPC they are maintained merely in the MME. Thereforein the NG system coordination and new procedures for the maintenance ofthe “CN-assisted (R)AN parameters” are needed.

This document proposes several variants how the session parametersmaintained in the SMF1 26 as shown in FIG. 7 and FIG. 8 can be used as“CN-assisted (R)AN parameters”:

-   -   (a) The SMF1 26 generates and sends a particular IE containing        the “CN-assisted (R)AN parameters” for a particular PDU session.        The RAN node 22 can determine the RAN parameters depending on        all activated PDU sessions and available “CN-assisted (R)AN        parameters” for other PDU sessions.    -   (b) The SMF1 26 sends session parameters towards the (R)AN node        22 as shown e.g. in step (7) in FIG. 7. The MMF 24 processes        some of those session parameters and determines the “CN-assisted        (R)AN parameters” to be signaled to the (R)AN node 22. In this        case, the MMF 24 is the main entity gathering and generating        “CN-assisted (R)AN parameters”.

One specific parameter of the “CN-assisted (R)AN parameters” set can bea parameter used for the transition from the MM Active to the MM Idlestate. Such a parameter can be a UE Inactivity timer. Another parametercan be a UP Session Inactivity timer. It is assumed that the UP SessionInactivity timer is part of the session parameters maintained by theSMF1 26, whereas the UE Inactivity timer can be maintained in the (R)ANnode 22 (or optionally by the MMF 24) as part of mobility managementcontext for the UE 20 as a whole, e.g. according to alternatives (a) or(b) above.

In case of session deactivation when multiple activated PDU sessions areexisting, the (R)AN node 22 can either 1) maintain an Inactivity timerper session (called UP Session Inactivity timer) and start a sessiondeactivation procedure after this timer expires, or 2) maintain a singleInactivity timer per UE (called UE Inactivity timer). In the lattercase, the (R)AN node 22 needs to align the value of the UE Inactivitytimer with the values of the multiple Session Inactivity timer. Forexample, the UE Inactivity timer obtains the value of the largestSession Inactivity timer value. A different logic in the RAN node 22 canbe also used to derive the value of the UE Inactivity timer based on theUP Session Inactivity timers.

Alternatively, the alignment of the Session Inactivity timer values maybe performed by the CCNF 24 (e.g. the MMF). In this case it is requiredthat the MMF 24 terminates the signaling from the SMFs and can processthe received session parameters like a Session Inactivity timer. The MMF24 can select a value for the UE Inactivity timer and signal it to the(R)AN node 22 within CN-assisted RAN parameters informational element.

Yet another aspect of the CN-assisted (R)AN parameters is theavailability of the new RAN mobility state called e.g. “RAN Inactivestate”. It is assumed that such a “RAN Inactive state” is managed by the(R)AN itself and it is transparent to the NG CN. From the NG CNperspective, the UE 20 would be in the MM Active/Connected state, andthe transitions between the RAN Active and RAN Inactive states would notinvolve any explicit signaling or awareness of the NG CN. This documentfurther proposes that the NG CN can assist the RAN with information forthe RAN Active and RAN Inactive states transitions. In this case, theCN-assisted (R)AN parameters contain parameters to be applied for thetransition for the RAN Active or the RAN Inactive states. For example,the CN-assisted (R)AN parameters can contain an additional Inactivitytimer, e.g. called a “RAN Inactive state timer” or a “RAN Dormanttimer”, which is used by the (R)AN node to derive a time point totransit from the RAN Active to RAN Dormant/Inactive state. With otherwords, the NG CN, e.g. the MMF 24, can indicate to the (R)AN node a “RANDormant timer” value. Such a timer value can be determined by the MMF 24based on UE subscription information, but also on currently activatedPDU sessions and considering their characteristics.

Solution 3

Another particular aspect of this document is the activation of the PDUsessions in case of multiple existing PDU sessions. Depending on the UEcapabilities, subscription information and/or other policies in thenetwork, the feature of independent activation of the PDU session may beomitted for certain UEs or in certain cases. In such a case, when aparticular SMF initiates the activation of a PDU session (i.e. UPconnection activation), a new procedure is proposed where the network(e.g. the MMF) assures that all existing PDU sessions are activated. Ina particular example, it is proposed that the MMF triggers a sessionactivation procedure towards the existing configured SMFs serving PDUsessions other than the PDU where currently UL/DL is to be transmitted.

More details for the case of DL data transmission are shown in FIG. 10.

The steps in FIG. 10 are described in detail as follows:

Step (0) to Step (3) are the same as in FIG. 9.

Step (4): Depending on the MM state of the UE 20 in the MMF 24 (e.g. theUE 20 can be in the Idle or in the Connected state), the MMF 24 performsdifferent procedures. For example, if the MM state is the connectedstate, as the NAS signaling connection and the NG2 signaling connectionexist, the MMF 24 forwards the SMF's request further to the (R)AN node22.

Otherwise if the UE 20 is in the MM Idle state (the case depicted inFIG. 10), the MMF 24 first checks the internal settings (e.g. UEcapabilities) for the particular UE. This is related to the newindication from the UE in step (1) in FIG. 7 exemplary called“individual SM activation”. If the CCNF 24 (e.g. the MMF), based on theUE's “individual SM activation” indication (has indicated“non-support”), is configured to activate all PDU sessions, the MMF 24sends an Activate session request to all existing (configured) SMFs forthis UE 20. The CCNF 24 (e.g. the MMF) maintains and stores allconfigured SMFs (and corresponding addresses and IDs) in the UE's MMcontext. In the particular case of FIG. 10, the MMF 24 performs theActivate session procedure towards the SMF2 27.

Step (5): The SMF2 27 activates the session with the UPF2 29 by sending(in needed) new session parameters over NG4 interface.

Step (6): After the SMF2 27 has contacted the UPF2 29, the SMF2 27replies step (4) by sending an Activation session response. The SMF2 27sends the session context parameters for PDU session 2 towards the (R)ANnode 22.

Step (7): If the UE's MM state is Idle (as assumed in this particularexample of FIG. 10), the MMF 24 first pages the UE 20 and later to setupthe UE context to the (R)AN node 22.

Step (8): After the (R)AN node 22 receives the updated UE contextparameters, which can be in the form of the session parameters sent fromthe SMF, the (R)AN node 22 establishes the new radio access connection(e.g. the radio access bearer) and updates its RAN parameters. Possibleupdate of the RAN parameters is described in solution 2.

After the (R)AN node 22 successfully establishes the radioconnection(s), the (R)AN node 22 informs the CCNF 24 (e.g. the MMF)about the success (or failure) and in addition informs the MMF 24 aboutthe RAN node UP identifiers (an IP address, tunnel endpoint identifiersfor each NG3 tunnel, etc.).

Step (9): The MMF 24 completes the session activation to the PDU session2. For example the MMF 24 sends a Session setup complete message to theSMF2 27 containing at least one or multiple of the following parameters:a UE ID, a session ID, RAN node UP identifiers (an IP address, tunnelendpoint identifiers for each NG3 tunnel, etc.).

Step (10): The CCNF 24 (e.g. the MMF) replies to step (3) by sending anActivate session response message to the SMF1 26. This message containsat least one or multiple of the following parameters: a UE ID, a sessionID, RAN node UP identifiers (an IP address, tunnel endpoint identifiersfor each NG3 tunnel, etc.).

Step (11): The SMF1 26 completes the session activation procedureinitiated by the UPF1 28 in step (1). The SMF1 26 sends e.g. a SessionActivation response message. This message contains at least one ormultiple of the following parameters: a UE ID, a session ID, RAN node UPidentifiers (an IP address, tunnel endpoint identifiers for each NG3tunnel, etc.), one or more session context parameters.

After the above procedures are successfully performed, the UPconnections (including a radio connection/bearer and a NG3 tunnel) forthe session #1 and the session #2 are established.

Similar procedure is applied to the scenario, where the UE 20 performs aService Request procedure to send UL data. In this case, when the MMF 24obtains the NAS MM signaling from the UE 20, the MMF 24 initiates thesession activation procedure towards all existing (configured) SMFs,instead of initiating the procedure to the SMF serving the PDU session,to which the UE 20 is about to send data.

Summary

Beneficially, the above described exemplary embodiments include,although they are not limited to, one or more of the followingfunctionalities:

1) A SMF is a dynamic repository for session parameters/context forexisting PDU session. Coordination between the SMF, the UE, the MMF andthe (R)AN node are needed to install the session parameters in the userplane functional entities.

-   -   a. The SMF derives and configures multiple types of Inactivity        timers in the UPF having different meanings.    -   b. The SMF serves as coordination point for Flow based QoS        architecture, namely the SMF installs the QoS marking rules to        the user plane function/gateway and signals to the (R)AN node        via control plane signaling (e.g. NG2) the rules how to process        the QoS marked packets.

2) In case of multiple UPFs per PDU session, different sets of sessionparameters are determined per UPF and maintained at the SMF.

3) The CN-assisted RAN parameters can be generated per PDU session bythe SMF. The determination of common RAN parameters based on themultiple session-oriented CN-assisted RAN parameters can be performedeither in the (R)AN node or in the MMF.

-   -   a. The SMF derives and configures multiple types of Inactivity        timers in the (R)AN node having different meanings.

4) [based on solution 3] A procedure triggered by the MMF, where the MMF(based on configuration to activate all existing PDU sessionsimultaneously) triggers all configured SMFs to initiate a sessionactivation procedure.

It can be seen that the above embodiments (e.g. solutions 1 and 2)describe a method for determination and exchange of session parameters,in case that multiple session may be available per UE, the methodcomprising the steps of:

1) The SMF retrieves session (e.g. DNN/APN-related) subscription ordynamically generated information from the U/SDM, the PCF or the SCEF.

-   -   a. In case the SMF obtains information via the SCEF, the SMF and        the SCEF discovers each other (in needed) and handshake during        session establishment.

2) The SMF derives or update or modifies session parameters (e.g. QoSrules, charging rules, QoS parameters and/or Inactivity timer(s))

-   -   a. The update of session parameters can be performed implicitly,        i.e. without retrieval of new information from other CN CP NFs.        For example, the SMF may store a communication pattern        indicating the different UE behaviour or Application behaviour        at various times of the day or week days.

3) The SMF sends currently valid session parameters to the (R)AN node(e.g. via the MMF). The SMF may also install at each session Activationsuch Session parameters to the UPF during session establishment, or sendthem to the UPF each time at session/NG3 activation.

-   -   a. Multiple types of Inactivity timer can be derived by the SMF        and configured in the (R)AN and/or in the UPF.

It can be seen that the above embodiments (e.g. solution 3) describe amethod for activation of PDU session where the mobility managemententity is configured to activate all existing PDU sessionsimultaneously, the method comprising the steps of:

1) A SMF initiates the activation of a PDU session;

2) A MMF initiates signaling to the rest of the existing SMFs toactivate the other PDU sessions.

3) All other SMFs trigger the procedure of PDU session activation.

Benefits

It can be seen that the above embodiments beneficially provide a numberof benefits, including (but not limited to):

minimized signaling between the RAN and the CN during a sessionactivation procedure; and

a novel method to activate a single or all PDU sessions based on UEcapability (Solution 3).

User Equipment (UE) 20

FIG. 11 is a block diagram illustrating the main components of the UE20. As shown, the UE 20 includes a transceiver circuit 50 which isoperable to transmit signals to and to receive signals from theconnected node(s) via one or more antenna 52. Although not necessarilyshown in FIG. 11, the UE will of course have all the usual functionalityof a conventional mobile device (such as a user interface 54) and thismay be provided by any one or any combination of hardware, software andfirmware, as appropriate. Software may be pre-installed in the memory 58and/or may be downloaded via the telecommunication network or from aremovable data storage device (RMD), for example. A controller 54controls the operation of the UE 20 in accordance with software storedin a memory 58. The software includes, among other things, an operatingsystem 60 and a communication control module 62 having at least atransceiver control module 64. The communication control module 62(using its transceiver control module 64) is responsible for handling(generating/sending/receiving) signaling and uplink/downlink datapackets between the UE 20 and other nodes, such as the basestation/(R)AN node 22 and the MMF 24. Such signaling may include, forexample, appropriately formatted signaling messages relating to radioand MM connection establishment procedures with the network (e.g. asession setup request and associated responses).

MMF 24

FIG. 12 is a block diagram illustrating the main components of the MMF24. As shown, the MMF 24 includes a transceiver circuit 66 which isoperable to transmit signals to and to receive signals from other nodes(including the UE 20) via a network interface 68. A controller 70controls the operation of the MMF 24 in accordance with software storedin a memory 72. Software may be pre-installed in the memory 72 and/ormay be downloaded via the telecommunication network or from a removabledata storage device (RMD), for example. The software includes, amongother things, an operating system 74 and a communication control module76 having at least a transceiver control module 78. The communicationcontrol module 76 (using its transceiver control module 78) isresponsible for handling (generating/sending/receiving) signalingbetween the MMF 24 and other nodes, such as the UE 20, the basestation/(R)AN node 22, and the SMFs 26/27. Such signaling may include,for example, appropriately formatted signaling messages relating to asession establishment/activation/modification procedure (for aparticular UE) and/or the like.

SMF 26/27

FIG. 13 is a block diagram illustrating the main components of anexemplary SMF 26/27. As shown, the SMF 26/27 includes a transceivercircuit 80 which is operable to transmit signals to and to receivesignals from other nodes connected to the SMF 26/27 (such as the MMF 24)via a network interface 82. A controller 84 controls the operation ofthe SMF 26/27 in accordance with software stored in a memory 86.Software may be pre-installed in the memory 86 and/or may be downloadedvia the telecommunication network or from a removable data storagedevice (RMD), for example. The software includes, among other things, anoperating system 88 and a communication control module 90 having atleast a transceiver control module 92. The communication control module90 (using its transceiver control module 92) is responsible for handling(generating/sending/receiving) signaling between the SMF 26/27 and othernetwork nodes (such as the MMF 24). The signaling may include, forexample, appropriately formatted signaling messages relating to asession establishment/activation/modification procedure (for aparticular UE 20) and/or the like.

(R)AN Node 22

FIG. 14 is a block diagram illustrating the main components of anexemplary (R)AN node 22. As shown, the (R)AN node 22 includes atransceiver circuit 94 which is operable to transmit signals to and toreceive signals from connected UE(s) 20 via one or more antenna 96 andto transmit signals to and to receive signals from other network nodes(either directly or indirectly) via a network interface 98. A controller100 controls the operation of the (R)AN node 22 in accordance withsoftware stored in a memory 102. Software may be pre-installed in thememory 102 and/or may be downloaded via the telecommunication network orfrom a removable data storage device (RMD), for example. The softwareincludes, among other things, an operating system 104 and acommunication control module 106 having at least a transceiver controlmodule 108. The communication control module 106 (using its transceivercontrol module 108) is responsible for handling(generating/sending/receiving) signaling between the (R)AN node 22 andother nodes, such as the UE 20, the MMF 24, and the SMF 26/27 (e.g.indirectly). The signaling may include, for example, appropriatelyformatted signaling messages relating to a radio and MM connectionestablishment procedure (for a particular UE 20), a sessionestablishment/activation/modification procedure (for a particular UE20), and/or the like.

MODIFICATIONS AND ALTERNATIVES

Detailed embodiments have been described above. As those skilled in theart will appreciate, a number of modifications and alternatives can bemade to the above embodiments whilst still benefiting from theinventions embodied therein. By way of illustration only a number ofthese alternatives and modifications will now be described.

In the above description, the UE, the MMF, and the SMF are described forease of understanding as having a number of discrete modules (such asthe communication control modules). Whilst these modules may be providedin this way for certain applications, for example where an existingsystem has been modified to implement the invention, in otherapplications, for example in systems designed with the inventivefeatures in mind from the outset, these modules may be built into theoverall operating system or code and so these modules may not bediscernible as discrete entities. These modules may also be implementedin software, hardware, firmware or a mix of these.

Each controller may comprise any suitable form of processing circuitryincluding (but not limited to), for example: one or more hardwareimplemented computer processors; microprocessors; central processingunits (CPUs); arithmetic logic units (ALUs); input/output (IO) circuits;internal memories/caches (program and/or data); processing registers;communication buses (e.g. control, data and/or address buses); directmemory access (DMA) functions; hardware or software implementedcounters, pointers and/or timers; and/or the like.

In the above embodiments, a number of software modules were described.As those skilled in the art will appreciate, the software modules may beprovided in compiled or un-compiled form and may be supplied to the UE,the MMF, and the SMF as a signal over a computer network, or on arecording medium. Further, the functionality performed by part or all ofthis software may be performed using one or more dedicated hardwarecircuits. However, the use of software modules is preferred as itfacilitates the updating of the UE, the MMF, and the SMF in order toupdate their functionalities.

The above embodiments are also applicable to ‘non-mobile’ or generallystationary user equipment.

Various other modifications will be apparent to those skilled in the artand will not be described in further detail here.

ABBREVIATIONS AND TERMINOLOGY

The following abbreviations and terminology are used in the currentdocument:

TABLE 1 3GPP 3rd Generation Partnership Project APN Access Point Name(used in 2/3/4G as identifier for various PDN connections. In 5G can besimilar to data network, DN) AS Access Stratum (use similar to RRCsignaling in this document) CCF Core Control Functions CCNF CommonControl Network Functions CPF Control Plane Function NB, Node B, evolvedNode B (but can also be any ‘RAN node’ eNB implementing 2G, 3G, 4G orfuture 5G technology) E- Evolved Universal Terrestrial Radio AccessNetwork (also UTRAN used as EUTRAN) GGSN Gateway GPRS Support Node GPRSGeneral Packet Radio Service HPLMN Home Public Land Mobile Network HSSHome Subscriber Server IE Informational Element (used as part of asignalling message) MME Mobility Management Entity MMF MobilityManagement Function MNO Mobile Network Operator NAS Non Access StratumNG Next Generation (term used for 5G networks, but may be any othergeneration of networks) NNSF NAS/Network Node Selection Function NSINetwork Slice Instances PCF Policy Control Function PCRF Policy andCharging Rules Function PGW Packet Data Network Gateway PSM Power SavingMode RAB Radio Access Bearer (used in similar way as Data Radio Bearer,DRB) RAU Routing Area Update RNC Radio Network Controller RRC RadioResource Control PLMN Public Land Mobile Network SCNF Slice-specificCore Network Functions SCS/AS Service Capability Server/ApplicationServer SMF Session Management Function SGSN Serving GPRS Support NodeSGW Serving Gateway TAU Tracking Area Update UE User Equipment UPF UserPlane Function (any UP function used for policy/QoS enforcement,mobility, UE's IP anchor, similar to SGW/ PGW in EPC) UTRAN UMTSTerrestrial Radio Access Network VPLMN Visited Public Land MobileNetwork

REFERENCES

-   [1] 3GPP TR 23.799 v1.0.2, 2016 September, “Study on Architecture    for Next Generation System”-   [2] 3GPP TS 23.401, v14.1.0, 2016 September, “General Packet Radio    Service (GPRS) enhancements for Evolved Universal Terrestrial Radio    Access Network (E-UTRAN) access”

This application is based upon and claims the benefit of priority fromEuropean Patent application No. EP 16193391.6, filed on Oct. 11, 2016,the disclosure of which is incorporated herein in its entirety byreference.

1. A User Equipment (UE) comprising: a memory storing instructions; andat least one processor configured to process the instructions to: send arequest message for a Protocol Data Unit (PDU) session establishment toa Session Management Function (SMF) node that sends, to a User PlaneFunction (UPF) node, a message comprising an inactivity timer fordeactivation of the PDU session and receives, from the UPF node,information of PDU session inactivity after a period specified by theinactivity timer, and receive, from the SMF node, a response message forthe PDU session establishment.
 2. The US according to claim 1, whereinthe request message is included in a Non-Access Stratum (NAS) message.3. A communication method of a User Equipment (UE), the methodcomprising: sending a request message for a Protocol Data Unit (PDU)session establishment to a Session Management Function (SMF) node thatsends, to a User Plane Function (UPF) node, a message comprising aninactivity timer for deactivation of the PDU session and receives, fromthe UPF node, information of PDU session inactivity after a periodspecified by the inactivity timer; and receiving, from the SMF node, aresponse message for the PDU session establishment.
 4. The communicationmethod according to claim 3, wherein the request message is included ina Non-Access Stratum (NAS) message.